This site details how certain conditions affect the boiling point of water; of particular interest are the first two entries, "salted water" and "hard water".

Yellowstone sits at an average elevation of about 8,000 feet above sea level. This means that the boiling point of water is about 197 degrees F. A high mineral content should increase the boiling point by at least 1-2 degrees, bringing it closer to 212 degrees. And any of those temps are well above the 160 degree critical threshold of a 1 second full-thickness burn in an adult.

The point is that to say "hot springs in Yellowstone get a lot hotter due to the mineral content and altitude" is not necessarily true. The hot springs could theoretically get hotter due to the mineral content raising the boiling point, but the altitude would tend to more than offset that, as your data shows. If mineral content increases the BP by a couple degrees but elevation lowers it to 197, then the BP ought to still be around 200, below the BP at sea level.

BUT, as you note, it doesn't really matter: well below boiling temperatures are sufficient to cause horrendous burns and could quickly be fatal if a significant portion of the body was immersed. So the affect on BP of minerals and altitude doesn't really have much to do with it, it's purely academic.